Method of using layered glassworking tool



Nov. 17, 1964 A. RNERo ETAL. 33

METHOD OF USING LAYERED GLASSWORKING TOOL Filed Feb. 14, 1952 INVENTOR$ 241V #10! n 4 5,? 0

J TTORNEY METHOD This invention relates to an improved tool or implementadapted to use'in contact with molten glass.

A material suitable for construction of a molten glass contacting and working t'ool must be able to withstand the high temperatures involved, for example1300 to 1600 C. 7 It might alsp have good physical and chemical stability in contactwith molten glass in order to avoid even a slight amountof erosion or solution in the glass. Refractory oxides of the type used in constructing melt,

ing units, such as aluminafare used to some extent, but are susceptibleto. both mechanical wear and chemical attack in'high melting temperature glasses. In these respects, platinum and platinum alloys have proven to I be particularly useful materials because of their generally inert characteristics. However, tools fabricated from these metals do not ordinarily have the inherent rigidity 'required to withstand application of force as in a forehearth plunger and/or stirring device or mechanism;

' Tools fabricated from molybdenum successfully'm eet this service condition, but undergo rapid oxidation at elevated temperatures. Such tools can not, therefore, be usedin' oxidizing. atmospheres, or in so-called oxidized glasses, unless effectively shielded. Accordingly, it ha'sbeen Patented Nave 1 1964 surface cladding, the molybdenum body; 'pdrtiori being characterized by a-ditfusible carbonlevel of less than 0.01% by weight carbon, Theiinvention' further resides in an improved method of producingsuch a 'glassworking tool which comprises maintaining the diffusible carbon level below such maximumamount. 1

' As is well known, carbon isnormally introduced into molybdenum during its production in order -to minimize oxygen embrittlement of the. metal. The residual carbon in the finished product may var considerably depending on production methods. Forexamplq 'an arc melted molybdenum is specified as normally containing a maximum,of0.04% by weight carbonwith a'low carbon-form available having a, maximum of 0.01% carbon. It has been found, however, that 'the carbon=levelcan be still further reduced by employing alternative reducing agents molybdenum proor by resorting to other methods of duction such as sintering.

In accordance with the present inventiongit would be desirable-to eliminate carbon completely, but this does 1 not appear to be either feasible or'necessary, Thus, it

has been found that consistently satisfactoryglassworb ing tools maybe produced with molybdenum having a carbon level of about 0.003 to 0.005%'by weight. Fun

ther, carbon contents up to about 0.01% may be tolerable. It will be appreciated that carbonaceous materials on the molybdenum"surface, such as oil, grease and the like,

will also contribute difiusible carbon. This in itself will normally raise the carbon level well above the tolerable .3'0-

limit/ Accordingly, extreme care must be taken to avoid such'carb'on contamination of the molybdenum during.

-- production and fabrication of glassworkingproducts.

proposed to fabricate glassworking 'tools, particularly on the glass contacting surface of the platinum. Actual .mcchanical failure of the tool appeared to result from development of a crack or failure in the weakened platinum cladding followed by oxidation and fracture of the underlying molybdenum structure at this point. The nature of this attack was rather puzzling inasmuch as simple platinum structures did not appear to be subject to" a similar attack.

In attempting to detect the possible source of such ;composite tool failures, it wasdiscovered that the presence of carbon in platinum, while the latter was immersed in molten glass, could produce a sirnilar type of porous structure in the platinum. Thev exact nature of the platinum attack is still not wellunderstood. It appears to involve oxidation of carbon diffusing to the platinum surface as well as possible reduction of glass ingredients with the reduced material entering the platinum and possiblydissolving in it. Further study revealed that residual carbon, normally present in molybdenum in varying amounts, was capable of diffusing out of the molybdenum into the platinum cladding; and rather rapstirrer mechanisms, from molybdenum and to apply aidly through the platinum to the glass contacting surface.

. Additional studies have indicated that this situation can be satisfactorily;controlled to permit production of composite platinun niolybdenuin glassworking tools providing the level of'fdiflusible carbon is maintained below certain limits;

The invention resulting from these studies is an im proved tool for use in contact with molten glass which comprises; a, molybdenum body portion and a platinum By way of further illustration of the' invention, refer ence is made to the accompanying drawings wherein,

FIGURE 1 is a perspective view of a forehearth needle or plunger, and y FIGURE 2 is a sectional view taken along line 2-2 of FIGURE 1. 1

A forehearth needle or plunger, as shown in FIGURE 1 and generally designated by numeral 10, is an elongated, cylindrical body adapted to having' its upper end 12 mounted above a glass tank forehearth for vertical reciprocating operation. The lower end 14 is of rounded or conical shape to cooperatively" function with a bottom outlet of such forehearth to discharge molten glass in successive charges or gobs by vertical reciprocation of plunger 10. The operating mechanism, forehearth str'ucture, and mounting means are not shown inasmuch as 'Q these are well known and form no part of this invention."

Forehearth plunger 10 merely exemplifies and illustrates a simple type of glassworking-tool to which the improv'ement of the invention is typically applicable,

In constructing composite plunger 10 in accordance with the present invention, amolybdenum core body 16,

having the general shape of the plunger, is initially fabricated. The mechanical fabrication of such molybdenum bodies is well known in the art. In accordance platinum alloy, such as platinum with up to 30% rhodium, in thicknesses of, for example, 30 mils. The cladding may be mechanically applied in strip form, conformed to the molybdenum core and pressure welded or filleted along the seams. This provides a sealed envelope that may then be carefully evacuated to remove air.

Care is taken to avoid carbon contamination during the further function as a glass stirrer or homogenizer.

process. Plunger 10 is then ready for mounting and operation in a glass melting unit or delivery chamber.

Plunger 10 may be so mounted as to be rotated as well'as reciprocated. In such case, the plunger may The invention is particularly useful in construction of more complicated stirring mechanisms such as shown in US. Patent Nos. 2,570,078, 2,570,079, and 2,831,664.

a The present invention has been described as having particular. utility 'in connection with fabricating glass delivery and homogenizing devices.

However, it will be understood that it has general utility in the fabrication of improved glassworking tools and devices of all types that come in contact with molten glass, particularly during the melting and delivery of such glass. Accordingly, the invention is subject to various modifications and forms within the scope of the appended claims.

. What is claimed is:

l. A method of producing glass comprising the step of bringing the glass, in a molten'state, into contact with a glassworking tool characterized by a molybdenum body portion, a platinum surface cladding, and a diffusible carbon level in the molybdenum body portion and at the molybdenum-platinuminterface of less than 0.01%.

t 4 I 2. A method of stirring glass comprising the step of bringing the glass, in a molten state, into contact with a glass stirring device characterized by a molybdenum body portion, a platinum surface cladding, and a diifusi-' ble carbon level in the molybdenum body portion and at the molybdenum-platinum interface of less than 0.01%.

'3. In the production of glass wherein molten glass is brought into contact with a glassworking tool fabricated from a molybdenum body portion provided with a platinum surface cladding, the improvement, whereby deterioration of the cladding is minimized, which comprises forming the body portion from molybdenum with a diifusible' carbon level below 0.01% and applying platinum cladding to the surface of the body while that surface is kept sufliciently free of carbon contamination to maintain the diifusible carbon level of the clad body below 0.01%.- 7

References Cited in the file of this patent UNITED STATES PATENIQ 7 2,315,565 Waltenberg -QLQApr. 6, 1943 2,401,040 Becker May 28, 1946 3,070,982 McGowan Jan. 1, 1963 a 

1. A METHOD OF PRODUCING GLASS COMPRISING THE STEP OF BRINGING THE GLASS, IN A MOLTEN STATE, INTO CONTACT WITH A GLASSWORKING TOOL CHARACTERIZED BY A MOLYBDENUM BODY PORTION, A PLATINUM SURFACE CLADDING, AND A DIFFUSIBLE CARBON LEVEL IN THE MOLYBDENUM BODY PORTION AND AT THE MOLYBDENUM-PLATINUM INTERFACE OF LESS THAN 0.1%. 